The present invention relates to a field effect semiconductor device such as an IGBT.
In recent years, in industrial devices and home electric devices, inverters have been advanced on a demand for saving energy. In order to answer the needs, an insulating gate bipolar transistor (to be referred to as an IGBT hereinafter) has rapidly spread. This IGBT is a kind of MOSFETs (MOS field effect transistors), and is a device in which a p-type layer is added to the drain of a MOSFET, and minor carriers are injected into the p-type layer to reduce the ON-resistance. Accordingly, the IGBT is a useful power device having merits such as gate voltage driving, high-speed switching characteristics, and unbreakable properties which are advantages of the MOSFET.
In general, upon completion of manufacturing a semiconductor wafer, the performance of the semiconductor wafer is checked in the wafer state. However, for example, when a forward voltage effect of the IGBT is to be measured, a current which can flow in the IGBT is regulated in relation to a measurement technique. For this reason, actually, measurement of the forward voltage effect of the IGBT is performed by a relative small current, and the forward voltage effect in an actual working current region should be predicted, so that the measurement precision cannot be avoided from being deteriorated.
In addition, when the IGBT is used, a feedback diode Bust be used. However, a forward voltage effect in a feedback diode is considerably related to the diode performance. For this reason, recognition of performance in a wafer state or feedback to manufacturing steps are very important. Also, in view of matter that the forward voltage effect is preferably made uniform when a plurality of elements are connected in parallel to each other, it is important to recognize the performance in the wafer state.
It is an object of the present invention to provide a semiconductor device for realizing measurement precision for forward voltage effect characteristics using a relatively small current.
The semiconductor device dealt with in this present invention includes a first conductivity type of semiconductor substrate, a first conductivity type of cathode region, a second conductivity type of first anode region, a peripheral region, and a marginal region. The first conductivity type of cathode region is formed on the lower side of the semiconductor substrate and has a cathode electrode formed on the lower surface of itself. The second conductivity type of first anode region is formed to partially constitute the upper surface of the semiconductor substrate and has an anode electrode formed on the upper surface of itself. The peripheral region is formed to surround the first anode region for assuring withstand voltage characteristics which are equal to or better than predetermined withstand voltage characteristics. The marginal region is formed to surround the peripheral region.
The semiconductor device in an aspect of the present invention further includes at least one second anode region formed in the first anode region, and an electrode formed on the upper surface of the second anode region. The second anode region is formed so as to be electrically isolated from the first anode region. The electrode is independent of the anode electrode on the first anode region.
Accordingly, measurement at a current density which is equal to or close to a rated current can be performed at a relatively small current.
In this semiconductor device, an upper surface area SA1 of said first anode region and an upper surface region SA2 of said second anode region satisfy a relationship represented by SA1 greater than SA2. The upper surface shape of the second anode region has radiuses of curvature of not less than 10 xcexcm at corners of the upper surface shape. An interval between said first anode region and said second anode region is set to be not less than 5 xcexcm.
The second anode region can be arranged at almost center of the first anode region. Further, a plurality of second anode regions can be formed within said first anode region, and the respective second anode regions can be arranged at different corners in the first anode region.
The semiconductor device in another aspect of the present invention further includes an almost annular second conductivity type of semiconductor layer arranged within the peripheral region and surrounding the first anode region, and an electrode formed on the upper surface of the semiconductor layer. The electrode is independent of the anode electrode on the first anode region.
Accordingly, measurement at a current density which is equal to or close to a rated current can be performed at a relatively small current. Additionally, when the semiconductor layer is formed in the peripheral region, the structure of the conventional first anode region can be used without changing the first anode region.
The semiconductor device in still another aspect of the present invention further includes an almost annular second conductivity type of semiconductor layer arranged within the marginal region and surrounding the first anode region, and an electrode formed on the upper surface of the semiconductor layer. The electrode is independent of the anode electrode on the first anode region. Accordingly, measurement at a current density which is equal to or close to a rated current can be performed at a relatively small current. Additionally, when the semiconductor layer is formed in the terminal region, the structure of the conventional first anode region can be used without changing the first anode region.
Furthermore, the semiconductor device in another aspect of the present invention further includes an almost annular first or second conductivity type of semiconductor layer formed within the marginal region and surrounding the first anode region, a second anode region formed within a region defined between the semiconductor layer and the corners of the body, and an electrode formed on the upper surface of the second anode region. The second anode region is electrically isolated from the first or second conductivity type of semiconductor layer. The electrode is independent of the anode electrode on the first anode region.
Accordingly, measurement at a current density which is equal to or close to a rated current can be performed at a relatively small current. Additionally, when the semiconductor layer is formed in the peripheral region, the structure of the conventional first anode region can be used without changing the first anode region.